1. Field
Embodiments of the invention generally relate to polyester-co-carbonate polyols and methods for producing the same.
2. Description of the Related Art
Liquid polyols which have excellent UV, hydrolytic, oxidative and chemical stability are required for various coating, adhesive, sealant and elastomer (C.A.S.E.). Polyester-co-carbonate polyols are either amorphous or liquid at room temperature and have excellent hydrolytic stability.
There are two existing routes for producing polyester-co-carbonate polyols. The most efficient route produces the desired product in a single reaction vessel by combining a polyol (alkyl diol, alkyl ether diol oligomer, etc), dialkyl carbonate, lactone, and catalyst in a reaction vessel under transesterification conditions. However, this procedure requires the ester functionality be derived by ring opening of expensive lactone monomers and precludes the use of readily available diacids because the water generated would deactivate traditional transesterification catalysts. In another route, the incorporation of less expensive diester functionality requires transesterification of preformed polyesters and polycarbonates. Typical cycle times for the production of polyesters on an industrial scale are approximately 24 to 36 hours. The production of polycarbonate from dialkyl carbonates on an industrial scale requires approximately 24 to 48 hours. Transesterification of the products requires an additional 6 to 10 hours. Therefore, the total cycle time would be 54 to 94 hours and does not account for transportation costs if the two processes cannot be accommodated at the same facility.
Therefore there is a need for more efficient and inexpensive methods for producing polyester-co-carbonate polyols.